Photographer: Jens Büttner/AP Photo

Snapchat Inc. has 150 million people using the service each day, said people familiar with the matter. That makes the four-year-old messaging app more popular than Twitter Inc. by daily active users.

Snapchat has been growing quickly, boosted by its popularity among young people. The app had 110 million daily users in December, said the people, who asked not to be named because they weren’t authorized to speak about the numbers.

Twitter, which was founded in 2006, has less than 140 million users interacting with the service daily, according to an average of analysts’ estimates surveyed by Bloomberg. The short-messaging service was once the largest social network after Facebook Inc. but has since been surpassed by Facebook’s other apps, including Instagram, Messenger, and WhatsApp.

Twitter has 310 million monthly active users, according to its most recent earnings report. The company doesn’t disclose how many of those people check in daily, but in the third quarter, it said about 44 percent of monthly users are active each day in the service’s top 20 markets. Twitter Chief Financial Officer Anthony Noto said at the time that the percentage had been stable but that “we’ll be sure to disclose” if there was a significant change. The company hasn’t given an update since then. This implies a daily active user count of 136 million. Twitter and Snapchat declined to comment.

Snapchat has made communicating more of a game by letting people send annotated selfies and short videos. It has allowed people to use its imaging software to swap faces in a photo, transform themselves into puppies, and barf rainbows. (In March, Facebook said it acquired the startup behind an app called Masquerade, which offers similar photo-manipulation tools.) Snapchat encourages people to visit the app frequently with features such as the "Snapstreak," which counts the number of consecutive days they’ve been communicating with their closest friends. Snapchat’s other content, such as news and Live Stories, disappear after 24 hours.

Messaging on Snapchat is “very modern,” Twitter Chief Executive Officer Jack Dorsey said on Wednesday at Recode’s technology conference. He acknowledged that Twitter at times can be confusing and alienating—something he’s trying to fix.